fopen and freopen

The SunOS 5.x and SunOS 4.1 versions differ in the handling of the a type. If mode a is specified, the SunOS 5.x version opens the file with O_APPEND set, while the SunOS 4.1 version doesn't. Also, the SunOS 4.1version always seeks to the end of the file when mode a is specified, while the SunOS 5.x version seeks to the end of the file if update mode is not specified.